1. Field of the Invention
The present invention relates to a method for producing an imaging device with an integral lens including an optical lens and a solid-state imaging element.
2. Description of the Related Art
FIG. 17A is a schematic exploded perspective view showing a structure of a conventional solid-state imaging device with an integral lens. FIG. 17B is a cross-sectional view of the conventional solid-state imaging device with an integral lens shown in FIG. 17A taken along line A-Axe2x80x2 of FIG. 17A. This solid-state imaging device is conventionally produced as follows. In a first step, a die bond is applied to a supporting mount 101 which is generally referred to as a package, and then a solid-state imaging element 102 is die bond-mounted on the package 101. In a second step, leads 103 provided on the package 101 are connected to electric signal I/O terminals (not shown) of the solid-state imaging element 102 by a wire bond. In a third step, recess portions 105 provided in a cylindrical member 104 of the package 101 are engaged with projecting members 108 provided on a support member 107 for supporting a lens 106. The support member 107 is moved toward the package 101 along an axis X and then turned about the axis X, so that the lens 106 is attached to the package 101. In order to achieve higher airtightness, an O-ring 109 may be provided between the support member 107 and the package 101. Such a solid-state imaging device with an integral lens is disclosed in, for example, Japanese Laid-Open publication No. 10-301009.
A solid-state imaging device receives light which has passed through an optical lens at a light receiving surface of a solid-state imaging element and outputs an image obtained at the light receiving surface as an electric signal. In order to obtain a satisfactory image, an optical axis of the light incident on the light receiving surface should not deviate from a vertical axis of the light receiving surface.
Referring to FIGS. 18A to 18E, a problem of a conventional method for producing a solid-state imaging device will be described below.
In the above-described conventional art, in order to mount the solid-state imaging element 102 on the package 101, the solid-state imaging element 102 is required to be bonded to the package 101 as shown in FIG. 18A. The parallelism of the package 101 and the solid-state imaging element 102 depends on: (i) the parallelism of a surface which is in contact with a die bonding stage (not shown), i.e., a bottom surface of the package 101 (shown as face C in FIG. 18B), and a bonding tool (not shown); and (ii) a quantity and position of a die bond 110 which is applied to a bonding surface (shown as face B in FIG. 18B) of the package 101. Therefore, in practice, there is great difficulty in placing a light receiving surface 111 (shown as face A in FIG. 18B) of the solid-state imaging element 102 in parallel with the bonding surface (face B) and the bottom surface (face C) of the package 101 with high precision.
There is a slight deviation from a vertical axis of the light receiving surface 111 due to tolerance included in each of the angles formed by: an internal surface (shown as face D in FIG. 18C) of the cylindrical member 104 of the package 101 in which a lens is attached and the bonding surface (face B shown in FIG. 18C) of solid-state imaging element 102; and a side surface (shown as face E in FIG. 18D) of the support member 107 and a center of the lens 112 (in a height direction).
When all these members are combined together, there arises a problem that an angle formed (denoted as F in FIG. 18E) by an optical axis 113 of the light passing through the lens 106 and the light receiving surface 111 of the solid-state imaging element 102 is deviated from the right angle.
According to the present invention, there is provided a method for producing a solid-state imaging device which includes: a first step of mounting a solid-state imaging element on a transparent substrate having a first surface and a second surface opposite to the first surface such that a light receiving surface of the solid-state imaging element is substantially parallel to the first surface and faces the second surface; and a second step of forming a lens holder on the first surface, the lens holder having a lens mounting surface substantially parallel to the first surface.
According to the above method of the present invention, a light receiving-surface of the solid-state imaging element is formed on the second surface of the transparent substrate having the first surface (light receiving surface) and the second surface. The lens is mounted and fixed on the lens mounting surface of the lens holder which is formed on the first surface (light receiving surface) of the transparent substrate. As a result, an angle of an optical axis of light incident on the first surface (light receiving surface) can be prevented from being deviated from an right angle.
In one embodiment of the present invention, the first step is performed by an ultrasonic wave connection technique.
According to the above method of the present invention, high throughput can be achieved even when a low temperature connection is used.
In one embodiment of the invention, the second step is performed by injecting resin into a mold.
According to the above method of the present invention, the lens holder is directly formed on the transparent substrate, thereby providing a smaller solid-state imaging device.
In one embodiment of the invention, the lens holder is formed integrally with a package.
According to the above method of the present invention, the lens holder and the package can be integrally formed, thereby producing a solid-state imaging device with an integral lens at low cost by using a small number of parts.
In one embodiment of the invention, the first surface of the transparent substrate is adsorbed airtight to the mold by vacuum suction.
According to the above method of the present invention, the transparent substrate can be fixed. A degree of vacuum can be measured before injecting the resin. Thus, a degree of inclination of the light receiving surface of the transparent substrate can be determined based on the degree of vacuum, thereby preventing defective molding of the solid-state imaging device. Moreover, there is a vacuum hole for vacuum suction formed in the lower mold, and a cavity is formed in the lens holder so that light passes therethrough.
In one embodiment of the invention, an O-ring is placed in the mold so as to be in contact with the mold and the first surface of the transparent substrate before injecting the resin into the mold.
According to the above method of the present invention, in the case where the vacuum hole is formed in the lower mold, even when the contact area between the transparent substrate and the lower mold is not sufficiently large, higher airtightness between the lower mold and the transparent substrate can be achieved to prevent resin flow.
In one embodiment of the invention, the method for producing a solid-state imaging device further includes the step of covering the solid-state imaging element with a resin between the first step and the second step.
According to the above method of the present invention, the airtightness between the solid-state imaging element and the transparent substrate can be secured for resin molding performed later.
In one embodiment of the invention, the method for producing a solid-state imaging device further includes the step of attaching leads for input and output of an electric signal to the transparent substrate between the first step and the second step.
In one embodiment of the invention, the method for producing a solid-state imaging device further includes the step of attaching leads for input and output of an electric signal to the transparent substrate after the step of covering the solid-state imaging element with the resin but before the step of performing the second step.
According to the above method of the present invention, leads having a desired shape can be provided to the solid-state imaging device, thereby facilitating the mounting of the solid-state imaging device on other devices.
In one embodiment of the invention, the transparent substrate is an optical filter.
According to the above method of the present invention, a solid-state imaging device using an optical filter can be produced.
Thus, the invention described herein makes possible the advantage of providing a method for producing a solid-state imaging device which can be easily produced and can prevent a shift in an angle formed by a light receiving surface of a solid-state imaging element and an optical axis of light incident on the light receiving surface through an optical lens so as to obtain a satisfactory image.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.